Core drilling for exploration purposes is usually performed with rock drill rigs, wherein the drill string components are placed in the active drill string position, lifted up from and lowered down into the drill hole with a winch. The winch wire is fastened to the uppermost drill string component with the aid of a lifting plug. Since core drilling aims to extract a drilled-out core of rock to be examined, tubular drill string components are used. During lifting of the drill string, which is performed frequently for exchange of drill bits, the string of tubes is lifted unit by unit, whereby the separate tubes are released from each other with the aid of the rotator device of the drill rig in co-operation with a lower tube holder.
Final release of a tube to be brought away from the drill string is today at least partly performed manually by the operators, this handling including final threading-off and lifting and guiding of the tube to an area of a tube magazine.
During lowering of the drill string, the working steps are performed reversely such that new drill string components in the form of tubes are successively lifted to a position where they are aligned with the drill string and threaded together by the operator. These working steps are straining for the operator and involve a risk of being subject to lifting and squeezing injuries for the operator which is not negligible.
Core drilling is often performed to very great depths, such as for example to drill length between 1000-2000 m. Because of the drill bit in operation being subject to wear, it has to be replaced relatively often, which results in that the entire drill string has to be lifted up from the drill hole, be dismounted into drill string components, the worn drill bit be removed and be replaced by a new one, whereupon the drill string can again be lowered down into the hole. Thereupon a further distance is drilled until the drill bit has to be replaced again etc. During the drilling, a flushing liquid swivel is connected to the uppermost end of the drill string for supplying flushing liquid for transporting away rock material having been disintegrated during drilling.